Extensive Field Documentation And Radiocarbon Dating

801 Words Aug 4th, 2015 4 Pages
Summary and conclusions
Extensive field documentation and radiocarbon dating resulted in a detailed alluvial history of mid-elevation valley and piedmont areas of the Carrizo Wash watershed. Much of the alluvial chronology has century-scale resolution, making it one of the best-dated and detailed Holocene alluvial sequences from the southern Colorado Plateau and the larger southwestern U.S. region. The Carrizo Wash alluvial history spans the entire Holocene, although early Holocene deposits in valley contexts are deeply buried with few exposures and little dateable material. Similarly, study of middle Holocene alluvial fan deposits was hindered by the rarity of exposed deposits of this age probably because of subsequent erosion.
Comparison of the Carrizo Wash alluvial history with regional flood histories and paleoclimatic proxies of the strength of winter (ENSO) and summer (NAM) moisture sources confirmed that Carrizo Wash geomorphic systems were sensitive to regional climate change throughout the Holocene. Channel entrenchment was usually preceded by extended drought and occurred more frequently during (1) periods of increased climatic variability associated with enhanced ENSO conditions, (2) major shifts in effective moisture or precipitation amount and seasonality, and (3) periods with few large floods. Accelerated piedmont and valley aggradation occurred during periods with low effective moisture associated with enhanced NAM and weak ENSO circulation that resulted in…

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